Hydraulic, Pneumatic & Fluid Power Systems worked example

Compressor Demand at 65% compressor isentropic and volumetric efficiency: a worked example

Here is what the math looks like when conditions slip. We hold every other input steady and drop compressor isentropic and volumetric efficiency to 65%, then walk the calculation through step by step. Calculate compressor demand for hydraulic, pneumatic & fluid power systems planning, quoting, troubleshooting, capacity review, or process improvement.

The inputs for this scenario

  • Total compressed air consumed (free air): 1,200 scf (held at the documented default)
  • Compressor runtime this period: 8 hr (held at the documented default)
  • Compressor isentropic/volumetric efficiency: 65 % (the input this scenario stresses; the baseline uses 90)

Working through the calculation

  • The calculation starts from the formula this tool documents: Raw compressor demand = completed output รท runtime.
  • Effective throughput works out to 97.5 units at these inputs, and this is the headline figure for the scenario.
  • Raw throughput works out to 150 units at these inputs.
  • Efficiency works out to 65 % at these inputs.
  • Runtime works out to 8 hr at these inputs.

How this compares with the baseline

  • Against the tool's baseline example, where compressor isentropic and volumetric efficiency sits at 90% and the headline result is 135 units, this scenario comes in 27.78% below the baseline at 97.5 units.
  • The practical read: the gap between this scenario and the baseline is entirely attributable to compressor isentropic and volumetric efficiency, so recovering it is worth quantifying in dollars before considering equipment or staffing changes. It assumes a single average flow and one efficiency value, so it will not capture peak transient demand, duty-cycle swings, or pressure-dependent compressor maps.

Results at a glance

  • Effective throughput: 97.5 units (headline result)
  • Raw throughput: 150 units
  • Efficiency: 65 %
  • Runtime: 8 hr

Run it with your numbers

  • To rerun this with your own numbers, open the live Compressor Demand calculator, set compressor isentropic and volumetric efficiency to your actual value, and adjust the remaining inputs to match your operation.

Last reviewed 2026-05-12.